If you feel like you've seen more of the northern lights painting the night sky lately, you'd be right — and there's an explanation for the uptick.
We're currently in a period of solar maximum, which is good news for aurora borealis enthusiasts, according to Ian Mann, a space physicist in the University of Alberta's Faculty of Science.
"If you want to watch beautiful shows of the dancing northern lights, solar max is an ideal time to do that," he says.
What is solar maximum?
The sun operates on a roughly 11-year cycle of magnetic activity, explains Mann. As the sun's magnetic field flips its north and south poles over this time, it switches between periods of lower magnetic activity (solar minimum) and periods of higher magnetic activity (solar maximum).
Surrounding the north and south magnetic poles of the Earth are regions referred to as the "auroral ovals" — areas where aurora displays typically happen. During periods of solar max, these zones tend to expand a bit closer towards the equator, moving into areas where more people live.
"There's more energy available, so they're more powerful, but they also move so they're at locations where they're more visible," says Mann. "It's a bit of a double whammy if you're an aurora chaser."
The period of solar maximum is also the perfect time to learn more about Earth and other planets in the solar system, explains Abigail Azari, an assistant professor in the departments of physics and electrical and computer engineering and a Canada CIFAR AI Chair and research fellow at the Alberta Machine Intelligence Institute. Her research seeks to better understand planetary space environments.
"Whatever is affecting Earth, dependent on its alignment, might affect other planets as well. So there are opportunities at this moment to do multi-planet studies and understand how unique — or not unique — Earth is compared with Mars, Venus, Mercury and other bodies in the rest of our solar system," she says.
Energy and colours galore
Before any colours appear in the night skies over Earth, things need to turn explosive — literally — on the sun.
The sun's surface is permeated by bundles of strong magnetic fields which poke out into the solar atmosphere. The ends of such magnetic loops represent cooler regions of the solar surface called sunspots, explains Richard Sydora, a professor in the Faculty of Science whose research focuses on understanding how the magnetic energy contained in those loops is converted into kinetic energy.
"Loops can be stable for days and then suddenly they'll explode and launch a whole mass of charged particles into space — that's called a coronal mass ejection," says Sydora. "It's basically a rapid release of the energy in these magnetic loops, but in the form of charged particles, which get a lot of kinetic energy and exceed the escape velocity of the sun's gravity field, blasting outwards into the solar system."
Earth's magnetic field typically deflects the majority of these blasts of charged particles, but during periods of intense activity, some manage to get through. Merging of the magnetic fields in the solar wind, arriving from the sun as a result of the expansion of its atmosphere into space, with the magnetic fields of the Earth inject energy into near-Earth space and power space weather and the dancing northern (and southern) lights.
In order to generate the aurora, accelerated particles, mostly electrons, rain down towards the Earth and then collide with atoms and molecules in the upper atmosphere, between 100 and 250 kilometres above Earth's surface, explains Mann. In the period after these collisions, when the particles drop back down into a lower-energy state, "they spit out a photon of light."
"You have these energy conversion processes occurring at the solar surface, but then you also have something similar occurring in Earth's magnetic field. That's ultimately the origin of the energy for accelerating the charged particles that rain into the Earth's atmosphere and cause this sort of glowing effect," says Sydora.
The palette of brilliant colours we see from the ground is a result of different gases involved in the collisions. Green, by far the most common hue, comes from particles colliding with oxygen atoms. Higher-energy collisions involving oxygen can have a red hue, and nitrogen is the gas responsible for blue and purple-tinted displays.
How — and when — to get the best view
If you have your sights set on experiencing as many northern lights displays as possible during this solar maximum, a good first step is to sign up for the U of A's Aurora Watch email alert service. AuroraWatch monitors geomagnetic activity in the Edmonton area and shares the percentage probability of witnessing an aurora display on any given day.
You may be able to spot some colours in the night sky from your backyard when there's a high enough probability, but for the best view, head to a darker area outside the city where light pollution won't interfere with the display. AuroraWatch advises that around midnight is often a particularly good time to keep your eyes on the sky.
If you happen to see a display that has a broader range of shades than the typical green-dominant showings, you may also want to pull out your camera for optimal viewing.
"Some of the purple or red colours can be quite difficult to see with the human eye because the eye is not very sensitive at those particular wavelengths," says Mann. Cameras — even the ones on your cellphone — are much more sensitive and able to pick out those wavelengths of light.
And as Mann highlights, patience is key. Sometimes you'll see nothing for a long stretch of time, "then suddenly there's a big release of this energy and the sky fills with this burst of dancing lights."
